Field of the Invention
The present invention relates to a rotary electric device for a power working machine, which is operatively connected to an engine as a power source for the power working machine such as a power mower and the like, and capable of being braked by a brake mechanism.
Description of the Related Art
As disclosed in, for example, Japanese Patent Application Laid-open No. 2005-282552, a technique has been known in which a brake shoe of a brake mechanism is placed in pressure contact with functional components, such as a flywheel and the like, which are operatively connected to the engine capable of driving a cutting blade, so that a crankshaft of the engine can be braked.
In the power working machine as described above, in a case where as an object to be braked by the brake mechanism, for example, a rotor of a rotary electric device, particularly, a yoke having a bottomed cylindrical shape, is selected in place of the flywheel, the brake shoe of the brake mechanism is placed in pressure contact with an outer peripheral surface of a cylindrical portion of the yoke. In this case, if the temperature of the yoke serving also as a brake drum is increased by frictional heat during braking operation, or the yoke is distorted or deformed due to braking load, problems such as deterioration in performance of the rotary electric device, damage to magnets, decrease in connection strength, and the like, may occur. Furthermore, if the temperature of the yoke as the brake drum becomes high due to heat generated from coils, the magnets and the like when the rotary electric device is operated, brake performance may deteriorate.
Examples of conceivable measures to counter the problems include: providing, between an inner periphery of the yoke and the magnets, a protection cover for preventing the magnets from being damaged and coming off; and increasing a thickness of the yoke itself so as to reinforce rigidity thereof and so as to hardly transmit heat thereto. However, both examples invite increase in manufacturing costs. Particularly, in the case of increasing the thickness of the yoke, there are problems such as increase in the weight of the yoke, accordingly increase in costs and deterioration in fuel efficiency, increase in inertial mass of the engine, and the like.